Importance

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Abstract

A low ink sensing system is combined with an ink cartridge detection system to enable a more efficient ink jet printer. An ink container which supplies ink to an associated printhead is modified by the incorporation of two light directing elements, in the preferred embodiment, a faceted prism and a roof mirror, into a transparent wall of the container housing. The cartridge, comprising the ink container and associated printhead, is mounted on a scan carriage. Periodically, the carriage is conveyed to a sensing station comprising a pair of light sources and a commonly used photosensor. A first light source is energized and a beam of light is directed to a location where the roof mirror, would be positioned if the cartridge is present. If the cartridge is absent, lack of a reflected return signal is sensed, indicating a cartridge has not been inserted. Print operation is halted until a cartridge is inserted. If a cartridge is properly inserted, the roof mirror returns most of the incident light to the photosensor which generates a signal indicating the presence of the cartridge. A second light source is then energized and directed towards the faceted prism, which is either immersed in ink or exposed to air within the interior of the container. If the latter, light is internally reflected by the prism facets back to the photosensor. If a print operation has been in progress, and the ink level has fallen, the common photosensor detects either a strong or weak redirected light component and initiates a status check and generates appropriate displays of low ink level or out of ink warnings.

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First Claim